Allylation ytterbium triflate

Indium-mediated allylation of the sugar derivatives in aqueous media proceeds with high anti diastereofacial selectivity in the presence of ytterbium triflate as a Lewis acid (Equation (18)).173... 

Allylation of aldehydes. Ytterbium triflate promotes the transfer of an allyl group from allyltributyltin to aldehydes at room temperature. Yields range from good to excellent (66-93%, 6 examples). 

Allylation of carbonyl compounds. Ytterbium triflate promotes the allylation... 

BiCfr [34b] proved to be a better catalyst than scandium [76] or ytterbium triflates [77] for this rearrangement which is also catalyzed by Bronsted acids [78]. Other functionalities such as Boc, allyl, and propargyl are compatible with bismuth catalysis (Section 11.2.6). 

Greeves e( al. reported that lanthanide triflates were effective for allylation of carbonyl compounds (20). Five mole percent of Yb(OTf)3 catalyzed the allylation of a series of aldehydes in good yield (Scheme 13.9) [20a]. Later they found a significant rate of acceleration by the Bronsted add in allylation of aldehydes with allyltributyltin catalyzed by ytterbium triflate (Table 13.9) [20b]. Recently, the concept of combined Lewis acid-Bronsted catalysis has attracted much attention from the chemical community because it often gives rise to significant improvement... 

In the presence of In powder 2-cycIohexen-l-one is converted by allyl iodide and Me3SiCI 14, in 63% yield, into the 1,4-addition product 2179 [84], which is also obtained in 73% yield by Sakurai 1,4-addition ofallyltrimethylsilane 82 to 2-cyclohexene-l-one in the presence of excess Me3SiCl 14 and catalytic amounts of InCl3 [85] (Scheme 13.25). Ytterbium] 111) triflate-catalyzed imino-ene reactions of N-tosylaldimines with a-methylstyrene are dramatically accelerated on addition of Me3SiCl 14 [85 a]. 

Consistent with the stability of the divalent oxidation states see Formal Oxidation State) of ytterbium and europium, the triflates of Yb(III) and Eu(III) are reduced by the bis(trimethylsilyl)allyl anion, leading to Ln(II) species (equation A) The same compounds can be made in higher yield by starting with Yb(II) and Eu(II) triflates directly. 

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